Implications:Incidence of PPC and important risk factors vary with study size and surgical population. Studies with >500 patients provide the most stable estimates of PPC incidence. The importance of several clinical risk factors for PPC is confirmed while other, traditionally held, factors do not appear important.

Impacts:For clinicians, this systematic review summarizes the evidence regarding preoperative pulmonary risk stratification before noncardiopulmonary surgery. For clinical and health services researchers, it provides clear direction regarding appropriate sample size and the minimum set of covariates to be considered in designing trials of interventions to prevent PPC.